Made from natural biopolymers such as proteins, polysaccharides and lipids, they form a thin edible layer on food surfaces that can extend their shelf-life. Cost, performance and consumer preferences will be the topics on which to play the future of these coatings.
Edible coatings are revolutionizing food preservation, offering a sustainable and effective solution: they reduce moisture loss, protect from oxidative damage and limit microbial growth, prolonging shelf life and preserving quality. These coatings can incorporate natural additives such as antimicrobials and antioxidants, improving their functionality and stability. In addition, they are biodegradable and can use by-products from the food industry, in line with the principles of circular economy and contributing to sustainability through the reduction of food waste and dependence on plastic.
Applications range from fresh produce, where breathing and moisture are controlled, to meat, dairy and baked goods, keeping their sensory and nutritional properties intact. Innovations in coating technologies, such as composites, nanoemulsions, and bio-nanocomposites, are improving mechanical strength, barrier properties, and compatibility with other preservation methods, such as modified atmosphere packaging. Although challenges remain in terms of cost, consumer acceptance and regulation, edible coatings represent a significant step toward sustainable food systems and a reduction in dependence on synthetic packaging.
Applications in food preservation
An essential advantage of edible coatings is their ability to control moisture loss, which is an important factor contributing to the degradation of fresh foods, such as fruits and vegetables. During storage, moisture loss leads to weight reduction, deterioration of texture and shrivelling. Polysaccharide-based coatings, such as those based on cellulose and pectin, form a semi-permeable layer that controls the evaporation of water, preserving the freshness of fruit and vegetables. In addition to moisture management, edible coatings act as an effective barrier against oxygen; a key factor in oxidative reactions that can lead to unpleasant tastes, discoloration and nutrient degradation. Lipid-based coatings, such as beeswax and carnauba wax, are particularly effective in limiting oxygen exposure.
These coatings are often applied to fruits such as apples, helping to slow down oxidation, prevent browning and minimize nutrient loss, thus improving both the visual appearance of the product and the market value over longer storage periods. Essential oils, such as thyme or rosemary, can be incorporated to prevent microbial growth. In the preservation of cheeses, thyme oil-based coatings inhibit spoilage micro-organisms and prolong their shelf-life. Similarly, fish products treated with chitosan-based coatings containing natural antimicrobials show a reduction in microbial spoilage and prolonged freshness.
Another positive aspect is the reduction of post-harvest food waste, delaying ripening and prolonging the freshness of sensitive products. In avocados, for example, coatings slow down ethylene production, slowing down the rapid ripening and deterioration during storage and transport. In addition, edible coatings may contain vitamins, probiotics and other health-promoting compounds. Fruit snacks topped with yogurt preserve fruit and provide additional nutritional benefits.
Types, composition, characteristics and functions of edible coatings
Edible polysaccharide coatings are widely used in the food industry and may incorporate polymeric components such as alginate, carrageenan, pectin, chitosan, starch or combinations of these polymers. These polysaccharides, from various natural sources, offer functional properties that improve food storage and safety. Proteins such as collagen, gluten, soy, milk and whey proteins, egg white, zein – a prolamin protein extracted from corn – may also be used for the formulation of edible coatings.
Collagen coatings have excellent moisture and oxygen barrier properties, which help inhibit microbial growth. Compared to polysaccharides, pure whey protein films have significant film-forming capabilities, increased physical strength and barrier properties. In addition, whey is rich in natural bioactive compounds, such as lysozyme, lactoperoxidase, lactoferrin and cysteine, which provide intrinsic antimicrobial and antioxidant benefits.
Lipid-based coatings, due to their water-repellent properties, reduce moisture permeability, helping to minimize water loss in perishable foods. However, they are prone to oxidative rancidification due to exposure to oxygen, resulting in unwanted sensory characteristics. In addition, lipids do not possess film-forming capabilities and intrinsic adhesive properties, limiting their direct application to certain food surfaces. However, it was found that these deficiencies can be overcome by combining lipids with other biopolymers, which improve film formation, adhesion and flexibility.
Innovations in physical-chemical and functional properties
New technologies applied to edible coatings are revolutionizing food preservation, going beyond traditional methods such as melting, extrusion, dipping and spraying. These key techniques are now enhanced by cutting-edge approaches, such as multilayer and nanostructuring, which significantly improve the protective capabilities of edible coatings. Multilayer adds complexity and increases coating durability, while nanostructuring offers unmatched control at molecular level, providing superior protection against environmental factors. In addition, we are witnessing the development of coatings with active, self-healing and superhydrophobic properties.
Active edible coatings, integrated with antimicrobial or antioxidant agents, offer increased safety, combating microbial growth and oxidation. Self-healing coatings add a layer of resilience, autonomously mending any damage thus maintaining the integrity of the protective barrier. Because of their ability to reduce water transfer, superhydrophobic coatings offer significant moisture resistance, resulting in longer shelf-life and freshness. Biopolymers, including widely studied hydrocolloids such as alginates and chitosan, are the gaining traction for these innovative coatings. These biopolymers, whether protein-based or polysaccharide-based, are hydrophilic, making them ideal candidates for food packaging. However, their properties can be further improved through reinforcement with nanoparticles, essential oils, and bio-nanocomposites.
These additions improve the physical and chemical characteristics of coatings, providing excellent levels of protection, functionality and sustainability. The use of nano-emulsions, water-in-oil or oil-in-water solutions represents an innovative approach to improving the physical and chemical qualities of edible coating formulations. The mechanism behind nanoemulsions involves the formation of nano-droplets, between 10 and 100 nm in size, coated with a film or layer of food ingredients, improving both bioavailability and chemical reactivity. Reducing the droplets size increases the surface area, amplifying the functional properties of encapsulated components, such as antibacterial essential oils, and improving the absorption of hydrophobic compounds.
This increased surface area correlates with higher antibacterial efficacy and extended shelf-life. In addition, the optical clarity of these droplets ensures that the coatings remain visually appealing while maintaining their effectiveness. The integration of essential oils into edible coatings via nanoemulsions is highly efficient, as it allows the use of small amounts of essential oils without seriously compromising the sensory properties of the food. Bio-nanocomposites are made of different nanocomponents arranged to create barriers against the penetration of molecules such as oxygen and water vapor, thus minimising weight loss and improving material durability. The effectiveness of polymer-based nanocomposites is significantly influenced by the concentration of the composite ingredients.
Applied to the development of edible coatings, nanocomposites improve the mechanical strength, barrier capacity, thermal stability, and antimicrobial properties of biopolymers. Inorganic nanoparticles, i.e. solid colloidal particles between 10 and 100 nm in size, have the ability to encapsulate functional molecules, thus improving their stability and performance. They also have significant antimicrobial properties, making them an ideal candidate for protective applications in food systems. Their incorporation into food matrices improves preservation by preventing microbial growth and minimising taste changes. 3D food printing, or 3D bioprinting, can also be used to create edible food coatings.
Ingredients such as fruit purées, vegetables, proteins and plant substances are extruded and deposited in a precise pattern to form a three-dimensional structure. When applied to edible coatings, 3D food printing offers the ability to design coatings with custom shapes and textures, enabling new features such as the controlled release of preservatives or the creation of protective barriers that extend the shelf-life and improve food quality. Despite its potential, the widespread adoption of 3D food printing for edible coatings faces several challenges. The high cost of 3D printers and ingredients, and the need for specialist knowledge in food material science are barriers to wider implementation.
Technology and commercial challenges
The adoption of edible coatings and films based on natural polymers is a promising solution for improving food safety and sustainability. Although these natural alternatives are safer and more environmentally friendly than synthetic options, they present difficulties. As the food industry increasingly relies on natural ingredients, further testing is essential to ensure that these additives consistently meet safety standards. The variability of natural compounds, which often leads to batch-to-batch fluctuations, requires improved quality control measures to ensure safety and efficacy in all product batches.
Consumer perception is another crucial issue in determining the commercial success of edible coatings. The commercial profitability of edible coatings is significantly influenced by the cost of sourcing high quality natural ingredients. Extracting these natural compounds can be expensive and difficult to standardize between production batches, which raises concerns about the cost-effectiveness of these coatings. The cost is not always justified, especially for some food products. The future of edible packaging lies in improving its performance, integrating advanced technologies and taking into account consumer preferences and industry needs.
